Half steps and whole steps

Twelve half steps make an octave, and only two pairs of white keys, E to F and B to C, are a half step apart.

The smallest step

Every interval in this course is built from one unit: the half step, also called a semitone. On a piano it is the distance from any key to the key right next to it, with nothing in between. That neighbour may be black or white. From C, a half step up is the black key C♯. From E, a half step up is the white key F, because there is no black key between E and F. An octave contains twelve half steps, which is why a piano has twelve different keys before the pattern repeats.

Two half steps make a whole step

A whole step, or whole tone, is two half steps. Most neighbouring white keys are a whole step apart, because a black key sits between them: C to D, D to E, F to G, G to A, and A to B. The two exceptions, E to F and B to C, are the places where the black-key pattern has a gap. To find a whole step above E, count two keys: past F to the black key F♯. A whole step above B is C♯. Whole steps can also start on black keys: from C♯, two keys up is D♯.

On paper, a half step can look like a whole step. E to F and F to G both move from a line to a space, one letter up, yet the first is one half step and the second is two. The staff shows letters; the keyboard shows half steps. That is why musicians learn both: letter distance tells you the interval's number, and half steps tell you its exact size. The next units build on that idea.

The major scale pattern

Play the white keys from C to the next C and you hear a major scale. Its steps follow a fixed pattern: whole, whole, half, whole, whole, whole, half. The two half steps fall exactly where the white keys have no black key between them, E to F and B to C. Start a major scale on any other note and you must use black keys to keep the same pattern. G major needs F♯; F major needs B♭. The "Ode to Joy" melody begins E, E, F, G: a repeated note, a half step and a whole step in its first four notes.

The scale that uses every key in order, all twelve half steps, is called the chromatic scale, from the Greek word for colour. Play it on the keyboard below, every key black and white from C to the next C. Then play only the white keys and listen for the two places where the step feels smaller. Guitarists meet the same idea on the fingerboard, where each fret raises a string by exactly one half step, so two frets make a whole step.